Field
This disclosure is generally related to solar panels. More specifically, this disclosure is related to a solar panel that is integrated with cell-level maximum power point tracker (MPPT) devices.
Related Art
A solar module/panel generally consists of individual solar cells that are electrically connected together in series. The serial connection of the solar cells increases the power and voltage output. For example, if n solar cells are connected in series, and are operating at exactly the same current and voltage, given that all of them have identical electrical characteristics and experience the same insolation and temperature, then the output voltage is n times that of an individual solar cell. However, one failed solar cell can significantly reduce the electricity generation of the entire module. In addition, power mismatch between electrically coupled solar cells can lead to drastic and disproportionate loss of power because the output current of the entire module is determined by the solar cell with the lowest output current. For example, when one solar cell is shaded while the remaining cells in the module are not, the power generated by the “good” cells can be dissipated by the shaded cell rather than powering the load. Shading of as little as 9% of a solar panel surface can lead to a system-wide power loss of as much as 54%. In some cases, the power mismatch can lead to a complete module failure (if safeguards like bypass diodes are not implemented).
Solar panel performance mismatch can be caused by a range of real-world phenomena, including partial shading caused by trees/handrails/chimney, bird droppings or debris, mismatch in cell/panel manufacture, lifetime degradation, differential aging/soiling, etc. Over time, the energy loss due to power mismatch among solar cells/modules can negatively impact the return on investment (ROI) of the solar array owner; weaken the economic rationale for solar power; and lead to installers and homeowners not utilizing roof space because of the shading and mismatch problems.
To overcome performance mismatch among solar cells within a module, a centralized form of performance optimization is carried out by an array solar inverter. Note that a large solar array often comprises individual solar panels that are connected in parallel. Typically, a series-connected set of solar cells or modules within a panel is called a “string,” and a set of parallelly connected strings is called a “block.” The array solar inverter receives DC current from each individual solar panel, and converts the DC current to AC. In addition, the solar inverter is configured to optimize the array's power generation by performing maximum power point tracking (MPPT) at the panel level.